Semiconductor processing typically involves depositing one or more layers of material and subsequently etching such layers to form a substrate feature. It is highly desirable to form uniform features over the entire surface of a semiconductor wafer. Yet, non-uniformities can arise based on the location of the feature relative to the wafer. For example, one type of semiconductor feature is a contact opening. Contact openings are typically etched through a dielectric material such as borophosphosilicate glass (BPSG). It has been observed that contact openings formed at or near the center of a wafer can have a different profile from contact openings formed away from the center of a wafer, e.g. at or near the wafer's periphery. Such non-uniformities are undesirable as they impart a degree of unpredictability in the finished integrated circuit.
This invention arose out of concerns associated with improving the uniformity with which substrate features, and in particular contact openings, are formed over a wafer. In particular, this invention arose out of concerns associated with improving dual-source plasma etchers and methods of using the same.